Method of endovenous laser treatment

ABSTRACT

A method of endovenous laser treatment is disclosed. An introducer sheath  40  is introduced into a vein and an optical fibre  12  is introduced through the introducer sheath until a first marking  45  on the optical fibre  12  indicates that the distal end of the optical fibre  12  is substantially in alignment with the distal end of the introducer sheath  40.  The introducer sheath  40  is then withdrawn relative to the optical fibre  12  until a second marking  46  on the optical fibre  12  indicates that the distal end of the optical fibre  12  extends a predetermined distance beyond the distal end of said introducer sheath  40.  Laser radiation is passed down the optical fibre  12  so that laser radiation is delivered to the inner wall of the vein and the introducer sheath  40  together with the optical fibre  12  are withdrawn a certain distance along the vein.

[0001] This application claims priority from U.S. Provisional PatentApplication Serial No. 60/369,256, filed Mar. 27, 2002. and from UKPatent Application Serial No. GB-01 14687, filed Jun. 15, 2001, theentire contents of each application being hereby incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a method of endovenous lasertreatment.

[0004] 2. Description of the Related Art

[0005] In certain invasive medical procedures thermal or other energy isadministered to a patient with beneficial effects. For example, energycan be used to detect a tumour or a region of the body, or to destroy ordenature diseased or malfunctioning body tissue. One example of thistype of treatment is disclosed in U.S. Pat. No. 6,095,149 whichdescribes the treatment of invertebral disc abnormalities with thermalenergy. Other types of medical treatment utilise laser energy, forexample endovenous laser treatment (EVLT), wherein laser energy isdelivered to the inner wall of a vein.

[0006] Laser energy may be delivered to an area of the body by means ofan optical fibre such as a bare-tipped optical fibre. However, the tipsof such optical fibres could cause trauma to soft tissues. Therefore,for some invasive applications it is not desirable to insert the opticalfibre directly into the body tissue. Instead, the optical fibre istypically inserted into a flexible introducer sheath which acts to guideand protect the optical fibre (and also the surrounding tissue) whilstit is being inserted into the region of the body to be treated. Anintroducer sheath is frequently inserted into body tissue over a guidewire and then the optical fibre can be inserted once the introducersheath is in place in the body.

[0007] In use the introducer sheath is often positioned so that theoptical fibre protrudes a few millimetres or centimetres from the end ofthe introducer sheath so as to deliver laser energy efficiently from thetip of the fibre to the surrounding tissue.

[0008] It is known to detect the protrusion of the optical fibre fromthe introducer sheath using ultrasound and/or direct visualisation of ared aiming laser beam from the optical fibre through the skin. However,these methods are unsatisfactory for a number of reasons. The use ofultrasound requires additional equipment which is expensive andcomplicates the procedure. Visualisation of the laser beam is impreciseand at best only a guide and then only in regions of the body which aresufficiently close to the surface of the skin. Therefore, conventionaltechniques are not suitable for use in a wide range of applications.

[0009] Furthermore, as a result of it being difficult for an operator orsurgeon to determine when the distal end of the optical fibre isapproaching the distal end of the introducer sheath, damage can readilyoccur to the soft tissues if the optical fibre is initially accidentallyextended beyond the introducer sheath. As a result an operator mustinsert the optical fibre very slowly into the introducer sheath and mustproceed cautiously at all times which makes the procedure slow.

[0010] It is therefore desired to provide an improved method ofendovenous laser treatment.

SUMMARY OF THE INVENTION

[0011] According to a first aspect of the present invention, there isprovided a method of endovenous laser treatment comprising the steps of:

[0012] (a) introducing an introducer sheath having a distal end and aproximal end into a vein having an inner wall;

[0013] (b) introducing an optical fibre having a distal end and aproximal end through the introducer sheath until a first marking on theoptical fibre indicates that the distal end of the optical fibre issubstantially in alignment with the distal end of the introducer sheath;

[0014] (c) withdrawing the introducer sheath relative to the opticalfibre until a second marking on the optical fibre indicates that thedistal end of the optical fibre extends a predetermined distance beyondthe distal end of the introducer sheath;

[0015] (d) passing laser radiation down the optical fibre so that laserradiation is delivered to the inner wall of the vein;

[0016] (e) withdrawing the introducer sheath together with the opticalfibre a certain distance along the vein; and

[0017] (f) repeating steps (d) and (e) a plurality of times.

[0018] The laser radiation which is delivered to the inner wall of thevein is absorbed and thermally re-structures the vein.

[0019] The first and second markings allow an operator or surgeon toknow when the distal end of the optical fibre is aligned with the end ofthe introducer sheath and when the distal end of the optical fibreextends beyond the introducer sheath by a predetermined amount. Thisenables the operator or surgeon to quickly insert the optical fibre intothe introducer sheath and enables the optical fibre to be positioned inthe optimum position relative to the introducer sheath without risk ofdamage to either the optical fibre or surrounding tissue.

[0020] The markings may comprise at least one band which extends aroundat least a portion of the circumference of the optical fibre.

[0021] Preferably, the two markings are separated by a distance ofeither about 4 cm, about 3.5 cm, about 3 cm, about 2.5 cm or about 2 cmso that in use the optical fibre will extend preferably between 2-4 cmfrom the end of the introducer sheath. A separation of approximately 3cm is particularly preferred.

[0022] The minimum preferred separation (2 cm) is so as to preventthermal damage to the introducer sheath during treatment. The maximumpreferred separation (4 cm) is so as to minimise the length of theoptical fibre remaining within the body once the introducer sheath hasbeen removed from the patient's body.

[0023] The two markings or markers may differ in shape and colour to aidthe operator or surgeon using the device. This can make it easier torefer to the markings, for example, when teaching or explaining how touse the device to another operator or surgeon.

[0024] The markings may be engraved or embossed on the optical fibre.This enables the operator to have tactile feedback as to the position ofthe markings, without having to look at the optical fibre. This allowsthe operator to concentrate on other equipment. Furthermore, if themarkings are embossed then there may be sufficient co-operation betweenthe marking and a friction seal of the introducer sheath so as to securethem temporarily together when the introducer sheath is retracted.

[0025] The laser radiation may be delivered either in a pulsed,continuous or quasi-continuous manner.

[0026] According to one embodiment, the introducer sheath may comprisegraduated markings for assisting a user to withdraw the introducersheath at a desired rate. This rate may be defined as a distance perunit time or a distance per laser pulse. A visual and/or audibleindicator may be provided to give an indication of how fast theintroducer sheath should be withdrawn.

[0027] The optical fibre is preferably secured to the introducer sheathat a position wherein the first marking is substantially in alignmentwith the proximal end of the introducer sheath. The optical fibre andthe introducer sheath may then be positioned at a desired location usingultrasound. The introducer sheath can then be released from the opticalfibre and the introducer sheath withdrawn relative to the fibre opticdevice until the second marking is substantially in alignment with theproximal end of the introducer sheath, enabling the distal end of theoptical fibre to protrude a known distance from the distal end of theintroducer sheath in order to administer laser energy. The optical fibremay then be secured to the introducer sheath substantially at theposition where the second marking is substantially in alignment with theproximal end of the introducer sheath, and energy from a laser energysource may then be provided to the distal end of the optical fibre. Theoptical fibre and the introducer sheath may be withdrawn whilst laserenergy is emitted from the distal end of the optical fibre. This is anadvantageous way of administering laser energy invasively.

[0028] According to a second aspect of the present invention, there isprovided a method of endovenous laser treatment comprising the steps of:

[0029] (a) introducing an introducer sheath into the Greater SaphenousVein having an inner wall;

[0030] (b) introducing an optical fibre having a distal end and aproximal end through the introducer sheath until a marking on theoptical fibre indicates that the distal end of the optical fibre extendsa predetermined distance beyond the introducer sheath;

[0031] (c) passing laser radiation down the optical fibre so that laserradiation is delivered to the inner wall of the Greater Saphenous Vein;

[0032] (d) withdrawing the introducer sheath and the optical fibre alongthe Greater Saphenous Vein a certain distance; and

[0033] (e) repeating steps (c) and (d) a plurality of times.

[0034] According to a third aspect of the present invention, there isprovided a method of endovenous laser treatment comprising the steps of:

[0035] (a) introducing an introducer sheath having a distal end and aproximal end into a vein having an inner wall, the introducer sheathhaving graduated markings;

[0036] (b) introducing an optical fibre having a distal end and aproximal end through the introducer sheath until a first marking on theoptical fibre indicates that the distal end of the optical fibre issubstantially in alignment with the distal end of the introducer sheath;

[0037] (c) withdrawing the introducer sheath relative to the opticalfibre until a second marking on the optical fibre indicates thatthe-distal end of the optical fibre extends a predetermined distancebeyond the distal end of the introducer sheath;

[0038] (d) continuously passing laser radiation down the optical fibreso that laser radiation is delivered to the inner wall of the vein; and

[0039] (e) withdrawing the introducer sheath together with the opticalfibre along the vein whilst laser radiation is passing down the opticalfibre.

[0040] According to a fourth aspect of the present invention, there isprovided a method of endovenous laser treatment comprising the steps of:

[0041] (a) introducing an introducer sheath having a distal end and aproximal end into a vein having an inner wall;

[0042] (b) introducing an optical fibre having a distal end and aproximal end through the introducer sheath until a first marking on theoptical fibre indicates that the distal end of the optical fibre issubstantially in alignment with the distal end of the introducer sheath;

[0043] (c) withdrawing the introducer sheath relative to the opticalfibre until a second marking on the optical fibre indicates that thedistal end of the optical fibre extends a predetermined distance beyondthe distal end of the introducer sheath;

[0044] (d) pulsing laser radiation down the optical fibre so that laserradiation is delivered to the inner wall of the vein;

[0045] (e) withdrawing the introducer sheath together with the opticalfibre along the vein;

[0046] (f) pulsing laser radiation down the optical fibre so that laserradiation is delivered to the inner wall of the vein; and

[0047] (g) withdrawing the introducer sheath together with the opticalfibre along the vein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Various embodiments of the present invention will now bedescribed, by way of example only, and with reference to theaccompanying drawings in which:

[0049]FIG. 1 shows a medical laser device;

[0050]FIG. 2 shows in greater detail the distal end section of theoptical fibre shown FIG. 1;

[0051]FIG. 3(a) shows an optical fibre having been initially insertedinto an introducer sheath and FIG. 3(b) shows the introducer sheathhaving been subsequently withdrawn relative to the optical fibre; and

[0052]FIG. 4 shows the optical fibre and introducer sheath used forendovenous laser treatment.

DETAILED DESCRIPTION OF THE INVENTION

[0053] With reference to FIGS. 1 and 2, an optical fibre 12 having adistal end 13 and a proximal end 15 is shown which is coupled to a laserenergy source 14 via a connector 22. According to one embodiment theoptical fibre 12 has a length of 3.5 m±0.1 m and is preferably providedwith a protective buffer layer 18. One or more markings or other form ofindicator 45, 46 are arranged on the optical fibre 12 at a predetermineddistance from distal end 13. Preferably, the markings 45, 46 areprovided around substantially the whole circumference of the protectivebuffer layer 18 of the optical fibre 12. According to the preferredembodiment, the laser energy source 14 is an 810 nm diode lasermanufactured by DIOMED, Ltd., United Kingdom. The connector 22 may beany suitable connector/fibre terminator such as a standard sub-miniatureA (SMA) connector (as shown) or other proprietary connector.

[0054] The distal end 13 of the optical fibre 12 is shown in more detailin FIG. 2. The optical fibre 12 is preferably capable of withstandingenvironmental temperatures of −10° C. to 120° C. and comprises a glasscore 32 with a fibre tip 34, a cladding layer 30 surrounding the core32, and an outer protective buffer layer 18. The core 32 has a higherrefractive index than the cladding 30 and thus laser energy is guidedalong the core 32 by total internal reflection. According to thepreferred embodiment the optical fibre 12 has a 600 μm diameter glasscore, for example Type FT600 URT, Spectram (SLT), No. BF05900 availablefrom 3M, USA. The buffer layer 18 is preferably partially stripped backa short distance (e.g approx. 1 cm) from the fibre tip 34 so that thediameter of the optical fibre 12 in the region around the fibre tip 34is approximately 0.6 mm. For efficient operation of the device thesurface quality of the fibre tip 34 is high. The fibre tip 34 ispreferably substantially free from defects within a central aperture of88% of the diameter of the fibre optic core 32 with all sharp edgeshaving been previously removed from the fibre tip 34. Preferably, otherdefects (if present) do not scatter light outside a 0.37 numericalaperture (NA), and do not cause localised heating when illuminated with60 W of laser light at 810 nm evenly distributed over a 0.37 NA. Theoptical fibre 12 is preferably capable of withstanding a force of 2 kg,applied between the connector/terminator (SMA) 22, and the distal end13, without damage.

[0055] The relationship between the position of the markings orindicators 45, 46 and an introducer sheath 40 or the like will now bedescribed in more detail with reference to FIGS. 3(a) and (b).

[0056]FIG. 3(a) shows the optical fibre 12 having been initiallyinserted within an introducer sheath 40 so that the distal end 13 of theoptical fibre 12 is substantially flush or otherwise aligned with thedistal end 60 of the introducer sheath 40. Marking 45 is shownsubstantially aligned with the proximal end 50 of the introducer sheath40. The introducer sheath 40 is then withdrawn relative to the opticalfibre 12 until marking 46 is substantially aligned with the proximal end50 of the introducer sheath 40. As shown in FIG. 3(b), the distal end 13of the optical fibre 12 then protrudes beyond the distal end 60 of theintroducer sheath 40 by a predetermined amount, preferably approx. 3 cm.

[0057] The introducer sheath 40 comprises a hollow tube 70 with afriction seal 42 at the proximal end 50 to prevent blood loss duringinsertion into blood vessels. The placement of the introducer sheath 40through skin and tissue provides access into an area to be treated, andacts as a guide for introducing instrumentation and other apparatus. Theintroducer sheath 40 is preferably a five French introducer sheath, suchas RCF-50-35-45-J-RB available from Cook, Inc., Bloomington, Ind.

[0058] Markings or indicators 45, 46 are preferably optically visualmarkings which are preferably provided around the whole circumference ofthe protective buffer layer 18 of the optical fibre 12, and are providedat predetermined distances from the distal end 13 of the optical fibre12. The predetermined distances are arranged to correspond topredetermined positions of the distal end 13 of the optical fibre 12relative to the distal end 60 of the introducer 40. The predeterminedpositions represent both alignment of the respective distal ends 13, 60as shown in FIG. 3(a) and also protrusion of the distal end 13 of theoptical fibre 12 beyond the distal end 60 of the introducer 40 as shownin FIG. 3(b).

[0059] In one embodiment the markings or indicators 45, 46 may beengraved or embossed onto the protective buffer layer 18 of the opticalfibre 12 surface. Advantageously, this enables an operator to havetactile feedback as to the position of the markings 45, 46 and thus havean indication as to the position of the optical fibre 12 within theintroducer sheath 40, without necessarily having to look at the opticalfibre 12.

[0060] The markings 45, 46 preferably comprise one or more bandsprovided at a number of predetermined locations and may preferably beprovided by heat shrinking material onto the optical fibre 12. The bandsare preferably 1 mm wide with ±0.5 mm tolerance. The bands arepreferably coloured in order to contrast with the colour of the bufferlayer 18. The number of bands can give information about the location.For example, one band may be provided as a first marker 45, and twobands for a second marker 46 etc.

[0061] The location of the first marker 45 preferably corresponds to adepth of insertion of the optical fibre 12 into the introducer sheath 40such that the distal end 13 of the optical fibre 12 (i.e. fibre tip 34)is very closely aligned or is substantially flush with the distal end 60of the introducer sheath 40. The introducer sheath 40 is preferably 35cm or 45 cm long and may be provided with a 2.1 cm friction seal 42making a total length 37.1 cm or 47.1 cm. Accordingly, the first marking45 may be provided at 371 mm±1 mm or 471 mm±1 mm from the distal end 13of the optical fibre 12.

[0062] The location of the second marking 46 preferably corresponds to aposition where the distal end 13 of the optical fibre 12 extends orprojects 30 mm±1 mm beyond the distal end 60 of the introducer sheath40. Accordingly, the second marking is preferably provided at 401 mm±1mm or 501 mm±1 mm from the distal end 13 of the optical fibre 12.

[0063] The markings 45, 46 may comprise any number of bands, colours, orforms for ease of recognition during a medical procedure, or be providedat other locations along the optical fibre 12 depending upon the lengthof the introducer sheath 40 and any friction seal that the optical fibre12 is required to cooperate with.

[0064] An example of a use of the medical laser device is for use inendovenous laser treatment (EVLT) in a human leg 100. This will now bedescribed in more detail with reference to FIG. 4. Local anaesthesiasuch as 0.3% or otherwise dilute lidocaine administered perivenouslyalong the Greater Saphenous Vein (GSV) 200 and ultrasound guidance, arepreferably used. Percutaneous entry into the Greater Saphenous Vein 200is made with a needle at point 150, 25-45 cm below the SaphenofemoralJunction (SFJ) 300. A 0.035″ (0.089 cm) J-tip guide wire is passed intothe Greater Saphenous Vein 200 and a five French introducer sheath 40 ispassed over the guide wire and up to the Saphenofemoral Junction 300.The guide wire is removed and a sterile 600 μm diameter core,bare-tipped optical fibre 12 is introduced into the vein 200 through theintroducer sheath 40 until the first marking 45 is aligned with theproximal end 50 of the introducer sheath 40 (which corresponds with theportion of the friction seal furthermost from distal end 60). Theoptical fibre 12 and the proximal end 50 of the introducer sheath 40 arethen fixed or held together. They are then moved together and positionedusing ultrasound guidance at a location about 1-2 cm below theSaphenofemoral Junction 300 within the Greater Saphenous Vein 200. Oncepositioned, the introducer sheath 40 is then released from the opticalfibre 12 and the introducer sheath 40 is withdrawn relative to theoptical fibre 12 until the proximal end 50 of the introducer sheath 40is aligned with the second mark 46 on the optical fibre 12. When theintroducer sheath 40 and the optical fibre 12 are in this position thenthe distal end 13 of the optical fibre 12 will extend approximately 30mm beyond the distal end 60 of the introducer sheath 40. This positionhas been found to be an effective position for administering laserenergy in EVLT treatment. An extension of 20 mm of the optical fibre 12beyond the end of the introducer sheath 40 has been found to be theminimum suitable distance for administering laser energy in EVLTtreatment without causing thermal damage to the introducer sheath 40.The optical fibre 12 and the proximal end 50 of the introducer sheath 40are then secured together with non-permanent means. Alternatively, ifmarking 45 is embossed then there may be sufficient co-operation betweenthe marking 45 and the friction seal 42 of the introducer sheath 40 tosecure them temporarily together. Pulsed 810 nm wavelength laserradiation from a laser energy source (not shown) is administered with apower of 10-12 Watts, in pulses of 0.8-1.0 second duration at 1 secondpulse intervals to treat the Greater Saphenous Vein 200. The introducersheath 40 together with the optical fibre 12 are then slowly withdrawnin preferably 2-5 mm increments whilst administering the laserradiation, and manual compression is applied over a red aiming beam inorder to achieve vein wall apposition around the laser fibre tip 34.

[0065] In an embodiment, the cycle is activated and deactivated by afoot switch or hand switch. The clinician is instructed to withdraw theintroducer sheath 40 2-3 mm between 1 second laser pulses. This processcontinues until the desired length of the vein has been treated.

[0066] In other embodiments the optical fibre 12 may be made ofmaterials or comprise material combinations other than glass so long asthe guiding properties of the core 32 of the optical fibre 12 aremaintained i.e. providing the core 32 has a higher refractive index thanthe cladding 30, and so long as the materials can operate in thetemperature range −10° C. to 120° C. For example any glass, plastic orhollow waveguide material could be used.

[0067] It will also be appreciated that the indicators or markings 45,46 may be ink markings and the colour of the markings 45, 46 may giveinformation about their location. For example the first marker 45 may becoloured differently to the second marker 46. Alternatively, accordingto less preferred embodiments, the markings 45, 46 may be radio opaqueand hence be capable of observation by non-optical means.

[0068] Furthermore, it will be appreciated that other introducer sheathscommonly used in the art in interventional cardiology andelectrophysiology procedures including angiography, angioplasty,stenting, atherectomy, temporary pacing, endomyocardial biopsies,transseptal catheterizations, electrophysiology studies, and RFablations could be used.

[0069] Another embodiment of the present invention is contemplated,wherein the laser provides a continuous rather than pulsed output. Thelaser may be activated by a foot or hand switch. Graduated markings areprovided on the external surface of the introducer sheath 40 to providecontrol for withdrawing the introducer sheath 40 at a prescribed rateand to indicate how far the introducer sheath 40 has been withdrawn fromthe patient's body. A visible and/or audible indicator may be providedso as to assist an operator to remove the introducer sheath 40 andoptical fibre 12 at a controlled speed. In one embodiment the visibleand/or audible indicator may form part of the laser system coupled tothe optical fibre 12. As an example, if the markings on the externalsurface of the introducer sheath 40 were placed at 1 cm intervals, thenthe audible and/or visual indicator might be activated once per secondthereby assisting a user to withdraw the introducer sheath 40 andoptical fibre 12 at a controlled speed of 1 cm/sec. An additionalgraduation on the introducer sheath 40 would therefore be revealed everytime the indicator bleeped and/or flashed.

[0070] This embodiment has the benefit of potentially providingbio-feedback to control the rate at which the introducer sheath 40 iswithdrawn. Furthermore, the continuous withdrawal results in a moreuniform illumination of the internal surface of the blood vessel.According to the previously described embodiment using a pulsed lasersource, the introducer sheath 40 and optical fibre 12 are withdrawn in astepped manner which may in some circumstances cause relatively highintensity regions of illumination at, for example, 2-3 mm intervalsalong the blood vessel. Any such potential problem is therefore avoidedby using a continuous laser source, providing graduations on theintroducer sheath 40 and withdrawing the introducer sheath 40 in acontrolled manner.

[0071] According to a further embodiment a visual and/or audibleindicator may also be used in conjunction with the previously describedembodiment which uses a pulsed laser source as an aid to withdrawing theintroducer sheath 40. This allows a hybrid approach wherein the opticalfibre 12 is withdrawn a longer distance e.g. 1-3 cm during a longerpulse-length. According to this embodiment, the laser source is operatedin a quasi-continuous mode.

[0072] It will be appreciated that the above described embodiments aregiven by way of example only and that various modifications thereto maybe made without departing from the scope of the invention.

What is claimed is:
 1. A method of endovenous laser treatment comprisingthe steps of: (a) introducing an introducer sheath having a distal endand a proximal end into a vein having an inner wall; (b) introducing anoptical fibre having a distal end and a proximal end through theintroducer sheath until a first marking on the optical fibre indicatesthat the distal end of the optical fibre is substantially in alignmentwith the distal end of the introducer sheath; (c) withdrawing theintroducer sheath relative to the optical fibre until a second markingon the optical fibre indicates that the distal end of the optical fibreextends a predetermined distance beyond the distal end of saidintroducer sheath; (d) passing laser radiation down said optical fibreso that laser radiation is delivered to said inner wall of said vein;(e) withdrawing said introducer sheath together with said optical fibrea certain distance along said vein; and (f) repeating steps (d) and (e)a plurality of times.
 2. A method of endovenous laser treatment asclaimed in claim 1, wherein said introducer sheath is flexible.
 3. Amethod of endovenous laser treatment as claimed in claim 1, wherein saidpredetermined distance is 2-4 cm.
 4. A method of endovenous lasertreatment as claimed in claim 1, wherein said laser radiation isdelivered in a pulsed manner.
 5. A method of endovenous laser treatmentas claimed in claim 1, wherein said laser radiation is delivered in asubstantially continuous manner.
 6. A method of endovenous lasertreatment as claimed in claim 1, wherein said laser radiation isdelivered in a quasi-continuous manner.
 7. A method of endovenous lasertreatment as claimed in claim 1, wherein said introducer sheathcomprises graduated markings for assisting a user to withdraw saidintroducer sheath at a desired rate.
 8. A method of endovenous lasertreatment as claimed in claim 7, wherein a visual indicator is used toprovide an indication of how fast the introducer sheath should bewithdrawn.
 9. A method of endovenous laser treatment as claimed in claim7, wherein an audible indicator is used to provide an indication of howfast the introducer sheath should be withdrawn.
 10. A method ofendovenous laser treatment comprising the steps of: (a) introducing aflexible introducer sheath into the Greater Saphenous Vein having aninner wall; (b) introducing an optical fibre having a distal end and aproximal end through the introducer sheath until a marking on theoptical fibre indicates that the distal end of the optical fibre extendsa predetermined distance beyond said introducer sheath; (c) passinglaser radiation down said optical fibre so that laser radiation isdelivered to said inner wall of said Greater Saphenous Vein; (d)withdrawing said introducer sheath and said optical fibre along saidGreater Saphenous Vein a certain distance; and (e) repeating steps (c)and (d) a plurality of times.
 11. A method of endovenous laser treatmentcomprising the steps of: (a) introducing an introducer sheath having adistal end and a proximal end into a vein having an inner wall, saidintroducer sheath having graduated markings; (b) introducing an opticalfibre having a distal end and a proximal end through the introducersheath until a first marking on the optical fibre indicates that thedistal end of the optical fibre is substantially in alignment with thedistal end of the introducer sheath; (c) withdrawing the introducersheath relative to the optical fibre until a second marking on theoptical fibre indicates that the distal end of the optical fibre extendsa predetermined distance beyond the distal end of said introducersheath; (d) continuously passing laser radiation down said optical fibreso that laser radiation is delivered to said inner wall of said vein;and (e) withdrawing said introducer sheath together with said opticalfibre along said vein whilst laser radiation is passing down saidoptical fibre.
 12. A method of endovenous laser treatment comprising thesteps of: (a) introducing an introducer sheath having a distal end and aproximal end into a vein having an inner wall; (b) introducing anoptical fibre having a distal end and a proximal end through theintroducer sheath until a first marking on the optical fibre indicatesthat the distal end of the optical fibre is substantially in alignmentwith the distal end of the introducer sheath; (c) withdrawing theintroducer sheath relative to the optical fibre until a second markingon the optical fibre indicates that the distal end of the optical fibreextends a predetermined distance beyond the distal end of saidintroducer sheath; (d) pulsing laser radiation down said optical fibreso that laser radiation is delivered to said inner wall of said vein;(e) withdrawing said introducer sheath together with said optical fibrealong said vein; (f) pulsing laser radiation down said optical fibre sothat laser radiation is delivered to said inner wall of said vein; and(g) withdrawing said introducer sheath together with said optical fibrealong said vein.